In order to calibrate the performance of sonar systems, the transmitted wave patterns and amplitude, as well as the receive sensitivity of the transducer elements, must be measured in water and compared to measurements taken by calibration equipment. However, there are numerous practical limitations that interfere with the ability to accurately measure the performance of the sonar system.
Larger sonar arrays tend to be many wavelengths across the front of the array. In order to quantify the performance of the array, measurements must be taken at a substantial distance from the array. Larger arrays require the measurements to be taken up to a kilometer away, necessitating an extremely large testing facility.
Sonar array calibration must also take into consideration complicated environmental variations that are regularly encountered in the field. For example, refraction and attenuation can be affected by the salinity and temperature changes of the water. Further, the characteristics of the array may change slightly over time. The sensitivity of the ceramic transducer can change with age. Electronics driving the acoustic array and interpreting the received signal may also drift over time. From a fault tolerance standpoint, it is important to monitor individual elements in the array for possible malfunctions.
The present invention relates to system and method for determining a calibration factor for acoustic arrays in a laboratory against a known standard and then applying the calibration factor in real-time to determine if the array and/or the system to which it is attached has maintained its expected level of performance.